I would think that your thermostat is stuck open if it doesn't get hotter than that during normal driving. You should probably check that out first as your engine won't run as well as it should like that. My 240D runs just above 80 all the time.

Just my 2 cents.

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Michael Roth

1982 300TDT Wagon
1982 240D Euro!, 4spd manual-Parts car now, dead engine
88 Jeep Grand Wagoneer-fixing up for offroading
1989 Ford F150 (rust bucket) For Sale!
1953 Dodge B-4F, 1 1/2 ton Stake Bed (new restoration project)